1. Department of Radiology and Nuclear Medicine; Radboud University Medical Centre; Nijmegen 6525 GA The Netherlands
2. Department of Respiratory Medicine; University Medical Center Utrecht; Utrecht 3584 CX The Netherlands
3. Fraunhofer MEVIS; Institute for Medical Image Computing; Bremen 28359 Germany
4. Department of Medicine; National Jewish Health; Denver CO 80206 USA
5. Division of Pulmonary, Allergy and Critical Care Medicine; University of Alabama at Birmingham; Birmingham AL 35294 USA
6. UAB Lung Health Center; University of Alabama at Birmingham; Birmingham AL 35294 USA
7. UAB Lung Imaging Core; University of Alabama at Birmingham; Birmingham AL 35294 USA